5-6 GHz Front End Low Noise Amplifier.

Proceedings ofIEEE20086th National ConferenceonTelecommunication Technologies and IEEE20082nd Malaysia ConferenceonPhotonics,26-27 August 2008,Putrajaya, Malaysia

5-6 GHz Front End Low

Noise Amplifier

M.HChe

Halim',

M. Z.A.

Abd

Aziz1' A. Rani Othman1, S.A Sahingan1, M.F Selamat1 and A.A

Abd

Azizl

Faculty of Electronic & Computer Engineering Universiti TeknikalMalaysia Melaka (UTeM)

LockedBag 1200,HangTuahJaya,75450 Ayer Keroh, Melaka,Malaysia

hafizzan @gmail.com,mohamadzoinol@utem.edu.my,rani @utem.edu.my,asreenanuar@gmail.com,cyconx1 @gmail

.com,faiesz84@gmail.com

Abstract -This paper presents 5-6 GHz front end Low Noise Amplifier applicationfor IEEE standard 802.11 system for WLAN application. This amplifier uses FHX76LP Low noise SuperHEMT devicedesignedfor DBSapplicationfromEudynaDevice USA Inc. This paper is present design and simulation of single stage LNA circuits. Asinglestage LNA hassuccessfully designedwith 26.92 dB forwardgainand1.32 dB noisefigure,which stablealongtheUNII frequencyband.

Keyword:Wireless LAN; Low NoiseAmplifier;Gain; Noise Figure;MatchingCircuit.

I. INTRODUCTION

The IEEE 802.11 standard is used as references. The Low Noise Amplifier (LNA) system should meet this standard requirement and should operate properly for WLAN Bridge system [1]. The main requirements of the LNA are the lowest possible noise figure (NF) with a reasonable gain. The general topology of the LNA consists of threestages: theinput matching network (IMN), the amplifier itself and the output matching network (OMN)

[2],[3],[4].

The 5.8 GHz wireless LAN market grows rapidly and offers various benefits to the user 5.8 GHz LAN technology supports multimedia services, real time voice and video transfer and other bandwidth intensive applications

[5].

This paper presents two different designs of aLNA at 5.8GHz. The circuit design starts from FHX76LP Low noise SuperHEMT device designed for DBS application from Eudyna Device USAInc amplifier using the microstrip technology. Itis the LNA that mainly determines the noise figure of the system. Low power dissipation and small integrated area are also some important factors that must be considered in the design of the devices for wireless applications [6]. Based on S-parameters of the transistor and certainperformancerequirements, a systematic procedure is developed for the design of LNA. In LNA design, the most important factors are low noise, moderate gain,

matching and stability [7]. Besides those factors, power

consumption and layout design size also need to be considered indesigned works.

The characteristic of this commercialize Low NoiseAmplifier areshowsinTable 1below

-Table 1: FHX76LP Characteristic

Component Parameter Value

Frequency Range 5000-6000 MHz

FHX76LP Associated Gain 12dB

NoiseFigure 0.4 dB

InputIP3 8dBm

OutputP1dB 9dBm

II. LNA Circuit Design A SinglestageLNA

A single stage microwave transistor amplifier can be modeled by the circuit in Figure 1 where a matching network is used both sides of the transistortotransform the input and output impedance ZA to the source and load impedance Zs and ZL. Themostusefulgain definition for amplifier design is the transducer power gain, which accountsbothsourceand load mismatch[8].

Figure1:Single StageLNA circuit

[image:1.613.325.576.542.678.2]

Various type of matching technique can be applied to implement the matchingnetwork. The lump element matching is selected for this research work. The purpose of the calculation process is to predict the result for LNA design. MATLAB is usedtosimplify the calculationprocess. The calculation process begins with S-parameter selection for frequency 5 GHz to 6 GHz. In this paper, S-parameter is selected at bias point Vds= 2V and Ids= 10 mA from data sheet.

B Stability Consideration

[image:2.613.327.566.170.458.2]

One of the most important factors in high frequency amplifier design istodetermine stability of the given bias point. Equations in Table 2 and Table 3 are used to determine the stability and stability circle of the amplifier.

TABLE 2

Stability determination by formula

(2)

r1

_OUT =

1'*

_L

S

₂₂

4S12S211rs

+12S21F5

1-1115s

By combining the two formulas above, reflection coefficient of input/output matching circuits can be calculatedby:

B1-

B12

-_41

C1

2

2C1

FLM

B2

-

B22 -41 C212

2C2

(3)

(4)

Where

Stability Criteria

Unconditionally K > 1 & A 1< 1 stable

Potentially unstable K > 1 & A> 1 or

K

<1

& A

l<1

StabilityFactor

K 1-I

SI

12 -I 22 12 +1A 12 21

S12S2211

Delta Factor A =

Si1

s22 -

SI2

21

TABLE 3

Stability determination by stability circle

S12S21

S12S21

Yin

-122

rout

12-1IS

-l

1

IA

12 S22 -1

A12

(Radius) (Radius)

C _(Sil

-

AS*22

)

C

(S

22

-

AS11i)*

I1s51

-IA 22 -IA

(Center) (Center)

Theinput and the outputcircuits should be matchedto deliver maximum power to the load. After stability of active device is determined, input and outputmatching circuits should be designed so that reflection coefficient of each port can be correlated withconjugate complex numberasgiven below:

B1 =1+

ISll

I'

-

S22

12 - A

12

(5)

B2

=1+1

22

12

-_

12

-

A

2

(6)

1C

= ₁₁ -

V22

(7)

C2

=

E22

-

VS11

(8)

v

=1

_{'11 22} -

1232

₁

(9)

The formulas above givesourceand load reflection coefficientstoobtain maximumpowergain.

C NoiseFigure andConstant NoiseCircle

Signals and noises applied to the input port of amplifier are amplified by the gain of the amplifier and noise of amplifier itself is added to the output. Therefore, SNR (Signal to Noise Ratio) of the output port is smaller than that of theinputport.The ratio of SNR ofinputport to that ofoutput portis referredtoas noisefigure and is larger orless than 1.Typically, noisefigure of 2-port transistor has a minimum value at the specified admittance given by formula:

GN ls opt

F

=

F.

₊ RN I

t-

12

GS

(10)

r - 8_ 12 21 L

FIN

=FS

=SII+

SIF

22 L

(1)

[image:2.613.68.291.265.589.2]

D Designfor minimum Noise Figure

Low noise amplifier is important for receiver because noise figure of the amplifier of receiver affects noise figure of the whole system. To get minimum noise figure using 2-port transistor, source and load reflection coefficient should match with

Fopt

and load reflection coefficient should match with

Fout

with a complex conjugate number

[9],[10]

as formula below:

Fs

-F

(11)

O74141

H5OGHz- 20GHz NWAI

KCS(cktCircui1)

H.OGHz

NVAM 580GHz

[image:3.612.45.301.177.299.2]

INA!

Figure 3: LNAstabilitycircle

FL =OUt S22

+S12S21 )

1-S11rs)

(12)

III. RESULT AND DISCUSSION

Fortheproposed single stage LNA shown in Figure 1, the simulation result is shown in Figure 2 to Figure 5. The design LNArequiredtwo 2V supply voltage andconsumes4.5mW. In thebeginning of the simulationprocess,the transistor is modeled in schematic using data sheet provided by manufacturer. The simulation result might not be accurate because the library has no data and modeled of the transistor FHX76LP Low noise SuperHEMT in Ansoft Designer. However. Duroid 5880 is being used as the microstrip substrate and the characteristic of this substrate. The comparison S-parameter simulated result as showninTable 3.

Ansoft Corporation XYPlot 2 Circuiti

08:ftS~

2000-.0o00 , ! I

5.0P 5..D 5.40 5..0 5.i

[image:3.612.61.301.453.656.2]

F[GHz]

Figure 4: LNAsimulation resultat5.80GHz

Y1

dB(K)

NWA1

IXY5.81 221

"

Min AnsftCorpration

Circuii

1tg-uoX

1.4-z

C3

1A40

'540 R '''6'

F[GHz]

Figure2: LNAstability Figure5: LNA noisefigure

138

Y1

dB(Sl1J

NWAl

XY:5.80 -1 5

____1_

dB(S21)

NVA1

XY: 5801 269

Y1 dB(S22) NVVAl XY:5.80H656

Y1

NF NWA1

XY885M136

Yi V

dB(S12) NVWA1

XY580-4T87

07:54:26 Y1

dBi'NF)

NA1

XY53032

5.40 6.0

F[GHz] 6.0

AnsoftCogrporaion

i

m

io

.3A

.

.m

[image:3.612.340.569.457.652.2]

[image:4.613.61.280.77.218.2]

TABLE 3

S-Parameter simulation result

A 5.8GHz low noise single stage amplifiers based on

FHX76LP Low noise SuperHEMT transistor was designed and

the prototype was tested at room temperature. At 2V collector bias on 5.8 GHz ,this LNA has noise figure 1.32dB, with input

return loss of -1.63dB, insertion loss of -47.90dB and output returnloss of -6.24dB. Usually,aslongasthestability factor and

delta factor are known as unconditionally stable, the stability

circle is necessarytobeproved because the amplifier is stableat

allareawithin the smith chart [9].

IV. CONCLUSION

The research work has yield a newLow Noise Amplifier

(LNA) circuit' design for frequency of 5.75 GHz to 5.85 GHz and circuit simulation were done in Ansoft Designer. LNA has

successfully simulated with 26.92 dB gain and 1.32 dB noise figureatfrequency 5.8 GHz

REFERENCES

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Cambridge University Press, 1998.

[3] B. Jung Jang,I.BokYom, S. Pal Lee (2001). "V-Band MMIC Low Noise

Amplifier Design Based on Distributed Active Device Model",

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[5] A. Parssinen, S. Lindfors, J. Ryynanen, S.I.Long, and K. Halonen, "1.8 GHz

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[6]D.M.Pozar(2000). "Microwave and RF WirelessSystem",United States of

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[7] G. Gonzalez (1997). " Microwave Transistor Amplifier: Analysis and

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[8] D. M. Pozar(1998)."MicrowaveEngineering",2ndEdition,United States of America: JohnWileyand Sons Inc.258-266,600-605.

[9] T.K.K. Tsang and M.N. El-Gamal, "Gain and frequencycontrollable sub-I V 5.8 GHz CMOSLNA,"inCircuits andSystems, 2002. ISCAS 2002. IEEE

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[10]E.H. Fooks and R.A. Zakarevicius (1990). "Microwave Engineering Using Microstrip Strips", Australia: Prentice Hall. 46,131-133.

139

Frequency S11 S12 S21 S22

5.75Ghz -2.27 -47.19 27.76 -7.26

dB dB dB dB

5.80Ghz -1.63 -47.90 26.92 -6.24

dB dB dB dB

5.85Ghz -1.15 -48.41 26.28 -6.18